The Pieces of the Puzzle:
Hello and welcome to yet another edition of my deranged ranting! As I promised You at the end of the previous chapter, this one is going to focus on another dōjutsu, namely the Mangekyō Sharingan. If You are asking me why not do the whole Sharingan, then my answer is that there is very little to nothing left for speculation concerning the "regular" Sharingan. On the other hand, the Mangekyō presents more than enough opportunities for speculation.
I have to warn You though. A good part of this is based on what Madara and Itachi told Sasuke and on the assumption that they were not lying.
Thoughts and Speculations Six: The Mangekyō Sharingan
The status of the Mangekyō Sharingan can be considered legendary because of its rarity, mysteriousness and power. It is not quite on the same level in this aspect as the Rinnegan because, frankly, nothing is but mentioning it in shinobi circles definitely inspires awe and respect. It is the final form of Uchiha clan's famed kekkei genkai that only five people ever achieved. They are, in order of acquisition, Madara, Izuna, Itachi, Kakashi and Sasuke. Since only one of these people, Kakashi, is not an Uchiha and he is referred to by his given name most of the time, I shall use only the given names of all Mangekyō Sharingan possessors.
According to what Itachi told Sasuke in chapter 385, Madara was the very first Uchiha to fully develop his kekkei genkai. The second person who achieved this feat was none other than Madara's very own bother, Izuna. The way Itachi told Sasuke the tale of the two brothers would indicate that they acquired their Mangekyōs in quick succession. Both Madara and Izuna were very skilled and regarded as the best amongst the Uchihas. Their development kept them on the same level, which would mean that they probably awakened their Sharingans at roughly the same time and also passed its evolution stages more or less simultaneously. I suspect that what Itachi said is true, that Madara indeed was the first of the two brothers to acquire the Mangekyō and I also suspect that he was the first in mostly everything, with Izuna following close behind. Madara is the evil one here and not only because of what his name means and it would make sense to me for him to be the first to taste the sweet, sweet power and fall prey to its corruption.
The third person to acquire the Mangekyō was the first person we saw present and use it, Sasuke's elder brother, Itachi. Although the method of how to acquire the Mangekyō became known after Madara and Izuna had achieved it, it took many decades of further trial and error for another Uchiha, Itachi, to emerge successful. After he slaughtered his fellow clansmen, it looked like there would be only one other person who would have the ability to develop the Mangekyō.
However, the fourth person to acquire the Mangekyō was not the one Itachi spared but his sensei; the only one of the quintuple to not be an Uchiha, Kakashi. Well, technically it was not only Kakashi but also his late friend Obito who got to the peak of Uchiha evolution. One could argue that it was only half a person or two people but let's not go there. Obito provided one eye and some essential blood, whilst Kakashi acted as the vessel that would develop and eventually perfect the gift. I wonder if Obito felt proud of his valiant friend, watching him from the Aether surpass many great Uchihas.
The last person to acquire the Mangekyō was Itachi's chosen one, his baby brother, Sasuke. Depending on whether or not he manages to eventually restore the Uchiha clan, he may very well indeed by the last one to reach that goal. Nevertheless, it seems that Sasuke obtained the Mangekyō reluctantly. He insisted on defying Itachi's "advice" and finding his own way of obtaining the strength necessary to defeat him – a way that would do without the acquisition of the Mangekyō. He partially succeeded because he managed to defeat Itachi without it but subsequently found himself in possession of it.
Well then, how exactly did these five men came into possession of this powerful tool? If I were in the possession of the secret scrolls hidden in the main temple of the Nakano shrine, I could tell You straight away but since I am not, I will have to speculate and base this off Itachi's words, events known from the manga and basic Sharingan facts. Itachi told Sasuke that the requirement to obtain the Mangekyō is killing Your closest friend. Since Itachi with the highest probability did kill Shisui, who was a very close friend and comrade of his, I do not doubt that Itachi did indeed obtain the Mangekyō this way. However, the ways through which the other members of the quintuple, sans Sasuke, obtained it are unknown and should be somewhat different from Itachi's method. Because Kakashi did not have a close friend to kill, the exact and universal method is probably simpler and less brutal.
I suspect that the method for obtaining the Mangekyō can be boiled down to extreme mental stress combined with great physical exertion. The same, only in a smaller dose, is needed to awaken the Sharingan and then to develop it through its commonly achieved stages. In Itachi's case, the mental stress came from the fact that he killed the person closest to him, barring his immediate family, with his own hands and from what he was about to do after that. The physical exertion was provided by Shisui who was at that time lauded as the most skilled Uchiha. He certainly did not go down without a fight.
Sasuke was the only member of the quintuple whose way towards the Mangekyō was faithfully recorded and presented to us on the pages of the manga. He obtained it after an arduous fight to the death with his brother Itachi and being forced to listen to Madara's tale of the Uchiha clan's demise. The battle drained him of almost all of his chakra and he looked to be on the verge of death. He saw it as not just killing his own brother but also the man largely responsible for his screwed up life. I would say that was enough mental stress but even if it was not, Madara's revelations surely did the trick. No matter how defiant and adamant Sasuke wanted to be, the little hesitations between Madara's words and his comebacks indicate that he gave it some thought and benefit of the doubt.
How Madara and his younger brother Izuna obtained their Mangekyōs is a mystery but logic would indicate that they both indeed found some people they were close to and killed them. However, I do not hesitate to say that it was most likely unintentional, at least on Madara's part, who was the first of the duo. Since both Madara and Izuna were the very first possessors of the Mangekyō, the Uchiha clan probably was not even aware that their kekkei genkai could be developed beyond the three-tomoe mature stage. The turbulent times before the system of Elemental Countries with one Hidden Village was established were probably rife with slaughter and fratricide more so than the current times and Madara and Izuna's position of power and influence was likely constantly targeted and contested. As to who exactly the brothers killed and what brought up the confrontation could be speculated upon for hours on end but I suspect that it was the people immediately below (or even above) the brothers in the chain of command of the Uchiha clan and that they had been through thick and thin together. The people who "served" the brothers' evolution either betrayed them in an attempt of a coup d'état or tried to assassinate them or both. My money is on the "both" alternative but Your guess is as good as mine, if not better.
Now we have come to the last person of the quintuple, the fourth in order of acquisition, Kakashi. I remember having read a fan-fic called "How It Could Have Happened" by lorelessbison, which was a very pathetic attempt at a humorous take on how Kakashi came into possession of his Mangekyō. I will not go there, I need to be serious here. Since the people Kakashi regarded as his closest friends were all already gone, at least that is what he told Sasuke, he had to have acquired his Mangekyō in a "regular" battle. When I was trying to think up a mentally and physically exhausting scenario for Kakashi, I came up with this. During the time-skip, he was probably sent on a long, solo, undercover, reconnaissance S-rank or A-rank mission to the Earth Country that may have lead him through the locales visited in Kakashi Gaiden. The enemy Iwa shinobi he encountered were probably "old acquaintances" out for blood and money. Since Kishimoto frequently uses the concept "history repeats itself", I think it is safe to say that the battle or battles Kakashi went through conjured up memories of that fateful night, especially those of Obito being crushed under a pile of boulders. Being a long way from home, in a hostile territory, engaged in a high-level battle and the demons of his past catching up to him once again was probably enough for Kakashi's left eye to evolve.
As You can see, I do not subscribe to the theory that "killing Your closest friend" is the only way of obtaining the Mangekyō. The situation is different for every Sharingan possessor. Just imagine an Uchiha with no real friends, not even among his or her clansmen, and with no immediate family. Such a person would inevitably have to find a different way of ascending the Uchiha evolution ladder. Of course, since there were only five people in recorded history who achieved it, his or her chances would be terribly close to zero but still not completely inexistent. Kakashi may be an excellent shinobi, a genius in his own right, but he was not an Uchiha, the Sharingan was implanted into him and, as I have mentioned, he did not have any friends to kill. He should be a good enough proof.
Now that the matter of acquiring the Mangekyō Sharingan has been thoroughly dealt with, it is time to discuss its cosmetic aspect. Every one of the six Mangekyō layouts that were presented in the manga has two common features. The first one is that they are all constructed from three points that previously were the three tomoes of the mature Sharingan positioned at the angle of 120 degrees between themselves and the other one is that those three points are joined in a circular pattern. The word "mangekyō" means "kaleidoscope" and also "mirror of 10 000 flowers", at least that is what the scanlation of chapter 385 says. Mangekyō Sharingan means the "kaleidoscope copy-wheel eye" and that speaks for itself. The transformation from regular Sharingan to Mangekyō takes the three tomoes and joins them in one uniform organised circle that at the same time retains the features of being a sum of its parts. I suspect Kishimoto may have drawn from the catholic principle of trinity, or triunity, here. Since most of the inspiration for the Rinnegan came from Buddhism, which is also a religion "alien" to Japan, and since Christianity has been present in Japan for a few hundred years, I think it does not sound that far-fetched. The three tomoes become one new entity and the one cannot exist without the three.
Out of all the six individual designs, I think that Itachi's Mangekyō looks the coolest. The three tomoes form a pattern that looks like a curved black shuriken with three points. It looks as if his pupil disappeared and was replaced by a "red hole" in the centre of the "shuriken". It is as if his eyes became hollow, colder, less human and definitely more menacing. This design is the best at emphasising the fact that the Mangekyō is a powerful ninja tool to be feared because it looks like a weapon. My second favourite design is Kakashi's/Obito's. Similarly to Itachi's Mangekyō, the tomoes form three black triangular points but they are not curved. Instead, from the tips of the triangles extend shapes akin to scythe blades and those connect the tips in a circle. The central part is also a "red hole". Kakashi's Mangekyō is definitely more elegant and intricate than Itachi's but it looks less menacing. I would go as far as saying that looking into Kakashi's Mangekyō would be pleasant, whilst looking into Itachi's would not be pleasant at all.
Sasuke's Mangekyō has probably the weirdest design out of all six. I have to confess that when I first saw his new eyes at the end of chapter 402, I did not make the connection. Seriously, those eyes being his new Mangekyō Sharingan was the last thing on my mind at that moment and it was only later when he used Tsukuyomi that I understood what was going on. I have not yet seen it officially coloured but that does not make deciphering the pattern that hard. The most apparent unique part of Sasuke's Mangekyō design is that the field, the iris, is not read but it is black. On that black field there are three pointy ellipses with black outlines that form a six-point red star. Contrary to Itachi and Kakashi, Sasuke's pupil is present at the centre of the pattern, instead of there being a "red hole". Although Sasuke's design still retains the feature of being composed of three parts, the individual tomoes are completely lost in it without a trace. Another thing that strikes me as unusual is that there is no defined circle. The intersections of the ellipses do form a shape akin to a circle around the pupil but that is only an approximation. Itachi's Mangekyō may lack a real circle as well but the "blades of the shuriken" are at least curved to invoke a sense of rotation. Unlike with the other designs, it is hard to imagine how exactly Sasuke's is formed. Furthermore, the more I look at it the more I find Sasuke's Mangekyō cute. Although Sasuke's "star" looks like a shuriken more than Itachi's Mangekyō in terms of outline, I do not find it unsettling at all.
Izuna's Mangekyō design is the blandest and least cool, in my opinion. It is just one thick black circle with a "red hole" in the centre and three thick black lines going outwards. I know I should blame Kishimoto instead of Izuna but that does not change anything. Madara's design, on the other hand is much more elegant. The tail parts of the three tomoes connected with the round parts of the neighbouring tomoes, creating a circle, whilst the round parts became hollowed out so there are three "red holes" on the circle. Just like with Sasuke's design, the pupil remains in the centre. These two designs combined to create Madara's eternal (or ultimate or final) Mangekyō Sharingan. That one retained all of Madara's features and the only influence Izuna's design had on it was the addition of the three thick lines going outwards from where the "red holes" were situated. I think that happened because it was Madara who "consumed" Izuna. Had it been the other way around, I assume that Izuna's design would be altered only by the addition of three "red holes" inside the black of his thick circle at the bases of the thick lines. Now that I think about it, that one would have been pretty scary.
If I am not mistaken, Kishimoto stated in the latest character data book that the Mangekyō Sharingan has a different design for everyone who attains it. I should not argue with "the God of all Naruto creation" but I feel I have to. The most glaring fact is that there were only five people with Mangekyōs and only six designs so far. Everyone should know that proving that something is wrong is much easier than proving that something is true. If You had a kaleidoscope as a child or still have one, You know that by turning it around You can get a great number of beautiful patterns. However, You have to admit that the number of possible combinations is finite. Because of that I think there is also a limited number of Mangekyō designs. You can use the counter-argument that since the Mangekyō Sharingan is a creation of Nature and not Man, the possibilities of its patterns should be endless due to the never-ending evolution and mutation. You can say that there may be hundreds, thousands or even millions of them. However, even if there are millions of them, I still think the number is finite here.
The other distinctive aspect of the Mangekyō is the powers that are bestowed upon its possessor. Just like the designs, they should be unique to every individual and limited in number. Those of You who have read the first chapter of this journal know that I think that the range of ninjutsu, genjutsu and fūinjutsu is unlimited. You are probably wondering why did I make the sudden 180 degree turn and why do I now assert that the number of techniques that can be obtained through the Mangekyō is limited. Well, I have started to doubt this myself but I decided to persevere. I think that the key problem with this is that the Mangekyō is limited to the Uchiha blood; I cannot say to the Uchiha clan because we all know about Kakashi. For a kekkei genkai to be strong, the blood must not be diluted too much. Over the ages and countless generations, the Uchiha clan developed a certain genetic make-up that is present in every member. That make-up made them look distinctive to the point when You can just look at a person and say "that is an Uchiha" or "that is not an Uchiha". That make-up made them fire specialists to the point that a child with a different affinity is a rarity. Kishimoto does not draw the Uchihas so similar to each other because he lacks creativity. I believe he does it because of this reason and maybe others unknown to me. This is Nature's problem. Overall and all around she can create countless life forms but when she is isolated and engineered, she can and will produce only limited results. That is my main reason why I believe that there is a limit to both the designs and the powers of the Mangekyō Sharingan.
I think there may also be a connection between the outward appearance of the Mangekyō and the powers it provides. It is time to use combinatorics again so do not say I did not warn You. Let me be generous and presume that there are 500 techniques in total that the Mangekyō can give its possessor. Of course, that person only has access to three out of the five hundred (see below). The simplest scenario is that the order of those three techniques does matter so for example a combination like 1-58-423 would be different from 423-1-58. In this case, the number of all possible combinations would be very high - 500x498x497 equals 124251000. That would be almost 125 million possible Mangekyō designs and that is A LOT but still a finite number.
You are now probably curious about the actual powers of the Mangekyō. Well, this is the best time to start talking about them. Studying Itachi closely, I discovered that the Mangekyō most likely gives its possessor three techniques and nothing more. One of these techniques is cast by the left eye, another by the right eye and the third one by both eyes at the same time. Correct me if I am wrong but there does not seem to be any other possible combination. I also think that there may be a connection between the number of techniques and the number of tomoes, since they are both three. Before the technique can be cast, the Mangekyō possessor needs to close the respective eye (or both eyes if s/he wants to cast the third technique) and focus chakra. The technique is then cast the moment the eye opens. This can be problematic because limiting even one of the senses (creating a blind spot) during battle can prove fatal, although the requirements to obtain the Mangekyō are so demanding that the possessor should already be skilled enough to eliminate this setback.
Itachi was the only one who we have seen perform all three techniques from his arsenal. I am sure that all of You know them well, although his third technique is known only to those who follow the manga; however, my ranting presumes that You are following the manga so it should not be a problem. Itachi's first technique is cast by his left eye and is called Tsukuyomi, which is the god of Moon from the Shinto pantheon. With this high-level genjutsu, Itachi is able to capture his victim in an illusion simply by locking eyes and the illusion lasts for 72 hours in the victim's mind, whilst in the real world it lasts only a few seconds. Itachi is the undisputed ruler of that illusory world and can do anything he pleases to the victim, including something pleasurable if he so chooses.
Itachi's second technique is cast by his right eye and is called Amaterasu, which is the goddess of Sun from the Shinto pantheon; she is Tsukuyomi's sister. According to one of the myths, Amaterasu shunned Tsukuyomi after he killed Uke Mochi and this was how night and day were separated and why the two siblings never saw each other ever again. I think this myth is one of the reasons why Kishimoto chose to name Itachi's one-eyed techniques that way. All right, back to shinobi reality. Amaterasu is a high-level Katon ninjutsu that creates all-consuming, inextinguishable black flames that converge on the spot where Itachi looks. With this technique, he can literally set things on fire with his mind.
The third and final technique, which we saw Itachi use only once, is cast with both eyes and is called Susano'o, which is the god of Sea and Storms from the Shinto pantheon; he is brother to Tsukuyomi, whom he eventually killed, and Amaterasu. I would classify this technique as a Kuchiyose because it conjures a semi-solid, demon-like creature that both protects Itachi with the Yata mirror and attacks his opponents with the Totsuka sword. This is another form of ultimate defence but unlike Gaara's sand and the Hyūgas' Hakkenshō Kaiten it actually is flawless, since it managed to protect Itachi even from that bolt of lightning. When Zetsu witnesses Itachi use Susano'o, he immediately recognises the two mythical items and notes that Orochimaru was searching for Totsuka no Tsurugi, since it is the only weapon capable of countering his Kusanagi no Tsurugi. The god Susano'o used Totsuka no Tsurugi to defeat the eight-headed serpent Yamata no Orochi and Itachi used the technique Susano'o to defeat Orochimaru's Yamata no Jutsu, draw him out of Sasuke and seal him away. I suspect he used this technique even during the Uchiha Massacre.
Although Kishimoto did a great job with naming these techniques and a raising interest in the Shinto mythology, I cannot understand why he switched Tsukuyomi and Amaterasu's positions. All three god-siblings were born when Izanagi washed his face clean of the grime of Yomi, the underworld. Tsukuyomi was born out of right eye and Amaterasu was born from the left eye, whilst Susano'o was born when Izanagi washed his nose. I shall return to this for a bit when I get to Sasuke's techniques.
Kakashi has been seen using only one Mangekyō technique and I think he cannot do any others because he has only one eye. The technique is called Kamui, which is the ancient Ainu term very close in meaning to the Japanese "kami" and it stands for a god, a deity or a divine spirit. Unlike with Itachi's techniques, there is no connection between the name and what the technique does, or at least I do not see it. Kakashi's Kamui is a space-time ninjutsu that targets what he focuses on with his Mangekyō and then sends it into another dimension. Which dimension precisely is not important but it can be the same dimension where sealed items are stored. It may have seemed that targeting Kamui is a lot of work but keep in mind that both Deidara and Kakashi were moving during the pursuit and that Kakashi had to keep his normal eye closed so his depth perception was not perfect. When Kakashi transported Deidara's exploding Nendo Bunshin, his only problem was accumulated exhaustion.
The true extent of Sasuke's Mangekyō is yet unknown and he can have anywhere between three and six techniques at his disposal. He was seen using only two techniques so far and both were the same as Itachi's: Tsukuyomi and Amaterasu. Only now, Sasuke uses Tsukuyomi with his right eye and Amaterasu with his left eye, which corresponds with the myths better. If we suppose that Madara was right when he said: "Somehow, at the last second, he transferred all his eye techniques into You," Sasuke should also have Susano'o at his disposal. The big argument here is whether Tsukuyomi and Amaterasu are really gifts from Itachi or if they are Sasuke's own techniques that came with his Mangekyō. If that were true, then there still could be a connection between the outward appearance of the Mangekyō and the powers it bestows upon its possessor but Sasuke would have only four techniques at the most: Tsukuyomi, Amaterasu, Susano'o and possibly his own two-eyed technique. In addition, it would be an argument in favour of my theory that there is only a limited arsenal of techniques the Mangekyō gives. However, since Sasuke is the second most important character in Narutoverse and since Naruto has grown extremely powerful, I suspect that he does have six Mangekyō techniques at his disposal, three from Itachi and three of his own. Trying to guess which technique would do what is somewhat pointless but if Itachi's repertoire is a blueprint for the arsenal that comes with a Mangekyō, then Sasuke's own techniques should be another genjutsu, another ninjutsu and either another Kuchiyose or a fūinjutsu. I did classify Susano'o as a Kuchiyose but it also had some sealing abilities.
I need to take a break from listing the individual abilities of the Mangekyō possessors and return to combinatorics again. I said that the simplest scenario takes into account the order of the techniques, which means what eye would cast which technique. If we assume that Sasuke has only Itachi's Mangekyō techniques, the difference between their designs would boil down to the fact that Sasuke uses different eyes for Tsukuyomi and Amaterasu, while Susano'o would remain the two-eyed technique. If the scenario was a bit more complicated in that the order of the three techniques out of five hundred would not matter, the number of possible combinations would diminish and it would be the binominal coefficient or "n over k". The result would be 20708500 - a little over 20 million possible Mangekyō designs. That is still a lot but it is also a lot less than 125 million.
However, I do not want to stop here. While it is apparent that the one-eyed techniques can be assigned to a random eye, as Sasuke proved, and that they should be equally demanding, the two-eyed techniques should be much more demanding and always assigned to both eyes, meaning that Susano'o cannot be used by only one eye. Therefore, let's assume that a certain number of those 500 theoretic Mangekyō techniques are exclusively two-eyed techniques. I think You will agree with me that one third of the whole, 166 techniques, would be a good guess and that the remaining 334 techniques would be one-eyed. In this case, the number of possible combinations would be 334x333x166, which is any combination of two one-eyed techniques paired with a random two-eyed technique. The result would be 18462852 possible Mangekyō designs. 18 and a half million may be very close to 20 million but it is still less and finite. I think that this scenario is the most likely of all. Of course, there is still the fact that Madara's eternal Mangekyō looks the way it does because it absorbed Izuna's and there is also a possibility that Sasuke's Mangekyō design was influenced by Itachi's gift. This would create billions upon billions other combinations and I get a headache just thinking about it. Maybe I should just give up and say that the number of Mangekyō designs is indeed infinite. However, when it comes to the actual techniques, I still think that their number is limited.
Now that the mathematical tangent is over, it is time to return to listing the Mangekyō powers. Izuna's three Mangekyō techniques are a complete mystery and there is absolutely nothing that could allow me to even guess. However, we may see them in the future because all of them should be alive in Madara's eyes. Madara himself can have up to seven techniques. If all of his own three techniques were different from Izuna's, he would have six at his disposal like Sasuke probably does but he even has one extra technique. Itachi says in chapter 386 that when Madara took his brother's eyes, it created a brand new technique. I strongly suspect that this mysterious technique is in fact the ability to suppress Kyūbi's malevolent chakra and control it. I am not exactly sure how to classify it but I think it can be called a fūinjutsu. Itachi also told Sasuke that this technique was made possible only by the fact that Madara took his brother's eyes, meaning someone from his immediate family. He may have just been full of himself but controlling Kyūbi is a monumental feat so obtaining such ability should be limited by similar severe restrictions.
This whole "controlling Kyūbi business" should be looked into a bit more. When Sasuke was sightseeing in Naruto's mindscape, he and Kyūbi had a little friendly conversation and the demon revealed that Sasuke's chakra felt almost as sinister as that of Madara. Sasuke then unceremoniously grabbed Kyūbi's nozzle, twisted it and dispersed the chakra that was leaking from the cage. This would indicate that even the regular mature Sharingan should be able to suppress Kyūbi's chakra as well at some level. I say at some level because Sasuke did not do it in the real world and Kyūbi was already greatly suppressed by being sealed inside Naruto. But to be sincere, my main reason for marginalising this is that I see no need in making the regular Sharingan or Sasuke even stronger then they already are.
The other known ability of Madara's is a space-time ninjutsu akin to Namikaze Minato's Hiraishin no Jutsu that allowed him to teleport freely and over huge distances. Whether or not his ability to partially phase in and out of existence is a part of this technique is up for debate but I find the two performances a little too different from each other. At the beginning of chapter 397, Madara was caught off guard by an Amaterasu Itachi implanted in Sasuke but he somehow managed to get rid of the inextinguishable flames when he stumbled back into darkness. I see only two possible explanations for this: either he was able to seal the flames like Jiraiya once did or he used another Mangekyō technique, which would be very similar to, if not the same as, Kakashi's Kamui. The possibility of a powerful Suiton jutsu is even more ridiculous than a fairy-tale.
Madara's eternal Mangekyō is named that way for two reasons. One is a confirmed fact and the other is probably just my own explanation. I will start with the reason I think I invented. I think Madara's Mangekyō is "eternal" because it granted him longevity that looks like immortality in the eyes of regular mortals. I somehow do not want to accept Madara being immortal. Hidan is immortal and Kakuzu found a way to regularly cheat death. Just because Madara decided to pluck his brothers eyes out in a fit of despair (or received them as a gift from his willing brother, depending on which tale You want to believe), that should not be enough to make him immortal. Of course, the probability of being a possessor of the Mangekyō and having a brother with the same gift is as small Tsunade's chances at winning a game of Old Maid but I still do not want to accept it. Madara simply acquired longevity in my book and that is my final word. Another reason for my disbelief is that Itachi wanted to pluck Sasuke's eyes out before they became Mangekyō and it could not be that easy either.
The confirmed reason for why Madara's Mangekyō is called "eternal" is closely connected with the only known weakness of it. The weakness is that once a person obtains the Mangekyō, he or she will inevitably begin a descent into eternal darkness – that is a fancy way of saying "they will go blind". This process is sped up exponentially every time a Mangekyō technique is used. It is a powerful tool that comes at a terrible price. Elite shinobi or those who were born blind should be able to eventually offset this handicap a little bit but if You pit together a blind shinobi and a healthy shinobi who is not stupid and knows how to take advantage of an enemy's weakness, the winner is clear. Well then, Madara found a way around this when he obtained Izuna's eyes. He did not do it knowing that he would find a source of eternal light, meaning that using his Mangekyō would no longer make him go blind, he simply wanted to see again. This is a good time to say that I think that Izuna was behind Madara in every aspect because once he found out about its weakness, he probably decided to use his Mangekyō less.
This is the "final secret" of the Sharingan Itachi mentioned in chapter 385 and elaborated upon in chapter 386. It is that You can obtain immeasurable power, including the ability to tame Kyūbi, avoid blindness for as long as You live and indeed live longer than Your fellow men ever could at the mere price of first killing someone very close to You, having Your brother do the same and then stealing his eyes. I still say that someone from Your immediate family – sister, mother or father – would do just as well but the problem is that it happened only once and will probably never happen again.
The last thing I need to discuss is the last of Itachi's cryptic messages. When he confronted Sasuke after he massacred the whole clan, he told him to go to the secret temple of Nakano shrine to discover the "true purpose" of the Sharingan. The word "purpose" is very vague. What is the purpose of any kekkei genkai? Well, there is of course the evolutionary purpose in Nature's Grand Scheme but is there really another purpose, a purpose justifiable in the world of Men? I think I am going overboard with this philosophising. I think the answer to this question is simply that "true purpose" and "final secret" are synonymous here. Being in possession of a kekkei genkai means that it should be used to the fullest of its capacity and in the case of the Sharingan, it is to do those horrible things mentioned above.
I think this is all I have to say on the matter of the Mangekyō Sharingan. I realise that a good part of this was just discussing and rehashing facts but I hope You will forgive me. I could have gone further by trying to invent Madara, Izuna and Sasuke's unknown techniques but I decided to leave that up to writers of real fan-fiction.
Piece It Together:
Well, there You have it folks, my longest chapter so far. I think You expect me write the next chapter on the Byakugan but that will not happen. There is absolutely nothing left to speculate about with that dōjutsu. Instead, You can look forward to one of these topics: the Bijū (that was one of the first topics I had in mind when I started writing this journal), souls (Edo Tensei, Shintenshin, Pain's abilities, there is a lot to explain) or Naruto's seal (Yin and Yang chakra, Shinigami, ties closely into the matter of souls).
Stay on the safe side!